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Cytogenetic relationships among Citrullus species in comparison with some genera of the tribe Benincaseae (Cucurbitaceae) as inferred from rDNA distribution patterns.

Li KP, Wu YX, Zhao H, Wang Y, Lü XM, Wang JM, Xu Y, Li ZY, Han YH - BMC Evol. Biol. (2016)

Bottom Line: The present study confirmed evolutionary closeness among cultivated watermelon (C. lanatus subsp. vulgaris), C. lanatus subsp. mucosospermus and C. colocynthis.Our result also supported that C. lanatus subsp. lanatus was not a wild form of the cultivated watermelon instead was a separate crop species.In addition, present cytogenetic analysis suggested that A. naudinianus was more closely related to Cucumis than to Citrullus or Acanthosicyos, but with a unique position and may be a link bridge between the Citrullus and the Cucumis.

View Article: PubMed Central - PubMed

Affiliation: Institute of Integrative Plant Biology, School of Life Sciences, Jiangsu Normal University, Xuzhou, 221116, China.

ABSTRACT

Background: Comparative mapping of 5S and 45S rDNA by fluorescent in situ hybridization (FISH) technique is an excellent tool to determine cytogenetic relationships among closely related species.

Results: In this study, the number and position of 5S and 45S rDNA loci in all Citrullus species and subspecies were determined. The cultivated watermelon (C. lanatus subsp. vulgaris), C. lanatus subsp. mucosospermus, C. colocynthis and C. naudinianus (or Acanthosicyos naudinianus) had two 45S rDNA loci and one 5S rDNA locus which was located syntenic to one of the 45S rDNA loci. C. ecirrhosus and C. lanatus subsp. lanatus had one 45S rDNA locus and two 5S rDNA loci, each located on a different chromosome. C. rehmii had one 5S and one 45S rDNA locus positioned on different chromosomes. The distribution of 5S and 45S rDNA in several species belonging to other genera in Benincaseae tribe was also investigated. The distribution pattern of rDNAs showed a great difference among these species.

Conclusions: The present study confirmed evolutionary closeness among cultivated watermelon (C. lanatus subsp. vulgaris), C. lanatus subsp. mucosospermus and C. colocynthis. Our result also supported that C. lanatus subsp. lanatus was not a wild form of the cultivated watermelon instead was a separate crop species. In addition, present cytogenetic analysis suggested that A. naudinianus was more closely related to Cucumis than to Citrullus or Acanthosicyos, but with a unique position and may be a link bridge between the Citrullus and the Cucumis.

No MeSH data available.


A scheme showing phylogenetic relationships among the Citrullus species
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Fig4: A scheme showing phylogenetic relationships among the Citrullus species

Mentions: Consist with previous studies [29, 30], the present FISH analysis demonstrated that the rDNA gene loci showed wide differences among the Citrullus species. C. lanatus subsp. vulgaris (cultivated watermelon) had same number and location of 5S and 45S rDNA loci to those in C. lanatus subsp. mucosospermus and C. colocynthis, but differed from those in C. lanatus subsp. lanatus. Our results are concordant with assumptions that the progenitor of the cultivated watermelon might be C. colocynthis [12, 13] and C. lanatus subsp. mucosospermus is the recent ancestor of C. lanatus subsp. vulgaris [29]. Several reports based on nuclear and plastid data of the genus Citrullus also confirmed evolutionary closeness among cultivated watermelon, C. lanatus subsp. mucosospermus and C. colocynthis. For example, the analyses of the sequence variation at cpDNA regions also confirmed the relationship because some of the C. lanatus var. lanatus accessions shared a unique substitution at the trnE-trnT region with all C. colocynthis accessions [40]. Schaefer et al. [36] also confirmed that the watermelon and C. colocynthis evolved from a common ancestor. Our results also supported Chomicki and Renner’ findings [4], which revealed that C. lanatus subsp. lanatus was not a wild form or progenitor of the cultivated watermelon but instead was a separate crop species, domesticated independently. In addition, present cytogenetic analysis showed that C. lanatus subsp. lanatus and C. ecirrhosus were more closely related to each other than they are to other Citrullus species. Based on the current FISH analysis and previous molecular phylogenetics [4] and cytogenetic studies [29, 30], a scheme about phylogenetic relationships among the Citrullus species was given (Fig. 4).Fig. 4


Cytogenetic relationships among Citrullus species in comparison with some genera of the tribe Benincaseae (Cucurbitaceae) as inferred from rDNA distribution patterns.

Li KP, Wu YX, Zhao H, Wang Y, Lü XM, Wang JM, Xu Y, Li ZY, Han YH - BMC Evol. Biol. (2016)

A scheme showing phylogenetic relationships among the Citrullus species
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4835933&req=5

Fig4: A scheme showing phylogenetic relationships among the Citrullus species
Mentions: Consist with previous studies [29, 30], the present FISH analysis demonstrated that the rDNA gene loci showed wide differences among the Citrullus species. C. lanatus subsp. vulgaris (cultivated watermelon) had same number and location of 5S and 45S rDNA loci to those in C. lanatus subsp. mucosospermus and C. colocynthis, but differed from those in C. lanatus subsp. lanatus. Our results are concordant with assumptions that the progenitor of the cultivated watermelon might be C. colocynthis [12, 13] and C. lanatus subsp. mucosospermus is the recent ancestor of C. lanatus subsp. vulgaris [29]. Several reports based on nuclear and plastid data of the genus Citrullus also confirmed evolutionary closeness among cultivated watermelon, C. lanatus subsp. mucosospermus and C. colocynthis. For example, the analyses of the sequence variation at cpDNA regions also confirmed the relationship because some of the C. lanatus var. lanatus accessions shared a unique substitution at the trnE-trnT region with all C. colocynthis accessions [40]. Schaefer et al. [36] also confirmed that the watermelon and C. colocynthis evolved from a common ancestor. Our results also supported Chomicki and Renner’ findings [4], which revealed that C. lanatus subsp. lanatus was not a wild form or progenitor of the cultivated watermelon but instead was a separate crop species, domesticated independently. In addition, present cytogenetic analysis showed that C. lanatus subsp. lanatus and C. ecirrhosus were more closely related to each other than they are to other Citrullus species. Based on the current FISH analysis and previous molecular phylogenetics [4] and cytogenetic studies [29, 30], a scheme about phylogenetic relationships among the Citrullus species was given (Fig. 4).Fig. 4

Bottom Line: The present study confirmed evolutionary closeness among cultivated watermelon (C. lanatus subsp. vulgaris), C. lanatus subsp. mucosospermus and C. colocynthis.Our result also supported that C. lanatus subsp. lanatus was not a wild form of the cultivated watermelon instead was a separate crop species.In addition, present cytogenetic analysis suggested that A. naudinianus was more closely related to Cucumis than to Citrullus or Acanthosicyos, but with a unique position and may be a link bridge between the Citrullus and the Cucumis.

View Article: PubMed Central - PubMed

Affiliation: Institute of Integrative Plant Biology, School of Life Sciences, Jiangsu Normal University, Xuzhou, 221116, China.

ABSTRACT

Background: Comparative mapping of 5S and 45S rDNA by fluorescent in situ hybridization (FISH) technique is an excellent tool to determine cytogenetic relationships among closely related species.

Results: In this study, the number and position of 5S and 45S rDNA loci in all Citrullus species and subspecies were determined. The cultivated watermelon (C. lanatus subsp. vulgaris), C. lanatus subsp. mucosospermus, C. colocynthis and C. naudinianus (or Acanthosicyos naudinianus) had two 45S rDNA loci and one 5S rDNA locus which was located syntenic to one of the 45S rDNA loci. C. ecirrhosus and C. lanatus subsp. lanatus had one 45S rDNA locus and two 5S rDNA loci, each located on a different chromosome. C. rehmii had one 5S and one 45S rDNA locus positioned on different chromosomes. The distribution of 5S and 45S rDNA in several species belonging to other genera in Benincaseae tribe was also investigated. The distribution pattern of rDNAs showed a great difference among these species.

Conclusions: The present study confirmed evolutionary closeness among cultivated watermelon (C. lanatus subsp. vulgaris), C. lanatus subsp. mucosospermus and C. colocynthis. Our result also supported that C. lanatus subsp. lanatus was not a wild form of the cultivated watermelon instead was a separate crop species. In addition, present cytogenetic analysis suggested that A. naudinianus was more closely related to Cucumis than to Citrullus or Acanthosicyos, but with a unique position and may be a link bridge between the Citrullus and the Cucumis.

No MeSH data available.